Shapes of molecules and their names

I understand that SF4 has 4BP and 1LP but I don't understand why it's called a trigonal pyramidal because I thought that trigonal pyramidal must have 3BP and 1LP. Also, I don't understand why the angle is 119⁰ and 89⁰

Reply 1

charco

Study Forum Helper

Original post by Bird1234

The atoms are arranged in a see saw (saw horse) arrangement. The central sulfur atom is at the apex of two trigonal pyramids. It is trigonal bipyramidal

(edited 5 months ago)

Reply 2

Bird1234

Original post by charco

The atoms are arranged in a see saw (saw horse) arrangement. The central sulfur atom is at the apex of two trigonal pyramids. It is trigonal bipyramidal

OK thank you I now understand the name but would the angle be 90 and 120 or would the lone pair affect the angle

Reply 3

charco

Study Forum Helper

Original post by Bird1234

OK thank you I now understand the name but would the angle be 90 and 120 or would the lone pair affect the angle

No, the trigonal pyramids are not regular. The lone pair of course affects the bonding pairs.
There is a whole page on it here: https://geometryofmolecules.com/sf4-lewis-structure-polarity/

Reply 4

Bird1234

Original post by charco

No, the trigonal pyramids are not regular. The lone pair of course affects the bonding pairs.
There is a whole page on it here: https://geometryofmolecules.com/sf4-lewis-structure-polarity/

OK thanks

Reply 5

Scanjo63

https://www.science-revision.co.uk/A-level_larger_molecules_with_lone_pairs.html

Try this link it may answer your question